1. Field of the Invention
This invention relates to a video signal recording/reproducing apparatus such as a video cassette recorder (VCR) for recording two component signals of a video signal on a recording medium such as a magnetic tape and reproducing the recorded signals.
2. Description of the Prior Art
The VCRs for industrial or broadcasting use are designed to record the so-called two-channel (2-ch) component signals of a video signal. The 2-ch component signals are usually a luminance signal and a time-base-compressed-modulated (TBCM) chrominance signal (hereinafter simply referred to as a chrominance signal). For preventing each of the 2-ch component signals from crosstalks between the two channels, a head for one of the 2-ch component signals has a different azimuth angle from that of a head for the other, and a guard band is provided between each adjacent two video tracks on a magnetic tape. This has been an obstacle to increase recording density.
To solve this problem, our previously filed patent application Ser. No. 890,347 (filed July 7, 1986), now U.S. Pat. No. 4,811,119, introduced a method to exchange the 2-ch component signals every nH (n: integer, H: horizontal scanning period) before converting (or frequency-modulating) the 2-ch component signals to recordable signals. That is, the 2-ch component signals are converted to two combined signals each containing the 2-ch component signals appearing alternately at periods of nH. The two combined signals are respectively frequency-modulated and recorded on a magnetic tape in a video track pattern in which each of the 2-ch component signals is aligned in a head width direction, i.e., a direction perpendicular to the longitudinal direction of each video track, so that the influence of crosstalks from an adjacent video track is eliminated. In reproduction, the recorded two combined signals are respectively frequency-demodulated before being exchanged every nH to obtain the 2-ch component signals.
This method has a problem that each of the 2-ch component signals is frequency-modulated or frequency-demodulated by two separate frequency modulators or two separate frequency demodulators. Therefore, the two separate frequency modulators or frequency demodulators must be severely adjusted to have a same performance in DC level, gain, linearity, etc. to accurately reproduce the original 2-ch component signals. Such an adjustment would be troublesome and costly. Further, even if the accurate adjustment would be completed, the performances of the two circuits would be changed by the environmental condition or the life of each circuit element. The performance difference between the two separate circuits for processing the two combined signals will cause a deterioration of the reproduced picture quality.